1. Field of the Invention
The present invention relates to a motion blur correction device and a motion blur correction method. In particular, the present invention relates to a motion blur correction device and a motion blur correction method by which motion blur correction can be performed during the playback of a video.
2. Description of the Related Art
While shooting video, it is preferable to use a tripod to avoid motion blur. However, tripods are not handy so people tend to shoot a video while holding their video cameras in their hands. The problem here is unintentional image blur (blur caused by hand movement) that is seen during the playback of a video shot as described above. Motion blur correction is a technology that reduces such motion blur and thereby improves the viewability of images. For example, Japanese Patent Application Laid-Open (Kokai) Publication No. 05-091396 describes a motion blur correction technology (hereinafter referred to as conventional technology) in which “video signals of an immediately preceding field and a current field are compared to determine a motion vector, and the clipping frame of an image to be outputted is moved in parallel with a direction opposite to the movement according to the motion vector, whereby motion blur is corrected”.
Note that there are generally two types of motion blur correction operations. One is for “still images” and the other is for “videos”. The motion blur correction in the present specification refers to the latter, or in other words, motion blur correction for videos.
FIG. 7 is a diagram showing the principle of motion blur correction. In FIG. 7, three images 1 to 3 shown in the top row are consecutive frames constituting a single video, and show the same person 4a to 4c, who is not moving, as a subject. Here, when the direction of motion blur while shooting this video is from the upper right to the lower left of the screen (refer to arrows 5 and 6) for descriptive purposes, the respective positions of the person 4a to 4c in the images 1 to 3 are shifted in an opposite direction to the motion blur. In other words, the position of the person 4b in the second image 2 shifts slightly to the upper right relative to the position of the person 4a in the first image 1, and the position of the person 4c in the third image 3 shifts further slightly to the upper right in relation to the position of the person 4b in the second image 2. Such shifts in the position of a subject appear as “blur” when the video is replayed, which is visually undesirable.
In short, in the motion blur correction of the conventional technology, the positions of the person 4a to 4c in the images 1 to 3 are aligned by a common clipping frame 7 being set in each of the images 1 to 3, and the images within the clipping frames 7 being outputted as motion blur corrected images 8 to 10.
The conventional technology is advantageous in that motion blur can be corrected during video playback. However, in the configuration of the conventional technology, motion blur correction is turned “ON” and “OFF” manually, and therefore there is a problem in that unnecessary processing is performed even when motion blur correction is not required.
That is, although frame rates for video imaging and playback commonly comply with television broadcast standards (about 30 frames per second in National Television System Committee [NTSC] standard), the imaging and playback are performed at special frame rates in the cases of, for example, high-speed imaging and slow-motion playback. During low frame-rate playback, the movement of the images is slow, and so viewability problems do not occur even when motion blur occurs to some extent. However, in the conventional technology, motion blur correction is performed even in such cases unless motion blur correction is turned “OFF” manually. Accordingly, unnecessary processing cannot be avoided, and power consumption is increased due to the processing.
In addition, motion-blur-corrected images, which are the images 8 to 10 within the clipping frame 7, are slightly smaller in size than the uncorrected images 1 to 3 (cross-hatched areas 8a to 10a surrounding the images 8 to 10 are made redundant) as shown in FIG. 7, and therefore there is a problem in that the provided imaging performance (imaging resolution) cannot be fully utilized.